Rubber bearings of the bush type, which are used, for example, in the automobile industry for mounting the components of the wheel suspension, for example, the suspension arms, comprise essentially a mostly hollow cylindrical, usually metallic inner part, an outer sleeve surrounding this inner part and an elastomeric bearing body, which is located in between and is connected to the inner part and the outer sleeve by vulcanization.
To affect the damping behavior, the so-called characteristic, it is, moreover, known that an additional reinforcing element is arranged in the elastomeric bearing body in bearings of this kind. The ratio of the radial characteristic to the torsional characteristic can be increased or the torsional characteristic can be reduced by means of this usually tubular reinforcing element, which consists mostly of a hard plastic or metal. A bush bearing with a tubular reinforcing element (intermediate tube) inserted into the elastomer is disclosed, e.g., in JP 07248422.
To obtain a bearing with good damping properties and especially long service life, it is necessary to generate a certain pretension in the elastomeric bearing body. This is achieved, in general, by reducing the diameter of the outer sleeve. However, without further measures, the reduction of the external sleeve diameter affects essentially only the area between the outer sleeve and the intermediate tube in bearings with a tubular reinforcing element. However, it is necessary for the reasons mentioned to generate a corresponding pretension, this may be done possibly as early as during the course of the manufacture, between the inner part and the reinforcing element inserted as an intermediate part as well. This is currently achieved in practice, e.g., by expanding the cylindrical inner part after the assembly of the bearing. However, this involves an additional step, which leads to extra costs. In addition, the fact that it is not possible to use high-strength materials for the insert part in this procedure can be considered to be disadvantageous.
A bush bearing of this type with a slotted intermediate tube is known from JP 08219210. It is possible due to this design to generate the pretension between the inner part and the intermediate tube as well as the pretension between the intermediate tube and the outer sleeve by calibration, i.e., by reducing the diameter of the outer sleeve. It is thus unnecessary to expand the inner part. According to that document (JP 08219210), the intermediate tube is either slotted through axially, or it has two longitudinal slots extending from a front side of the part over about ⅔ of its axial extension. The fact that the pretension that may be produced is not distributed uniformly over the circumference of the bearing body can be considered to be disadvantageous in the first-named embodiment with a through longitudinal slot. It would be possible to avoid this drawback by means of a plurality of slots distributed over the circumference. However, the reinforcing element would now consist of a plurality of parts, which would make it markedly more difficult to insert these parts into the injection mold for pouring with the elastomer. To avoid this, the second embodiment described in the document (JP 08219210) has two slots, which are located opposite each other on the circumference and start from a front side of the part, but are not through slots. Even though a more uniform pretension is thus achieved in relation to the circumference of the bearing body, this leads to the drawback that the pretension is not distributed uniformly in relation to the axial extension.